A driving force today in the electronics industry is to provide the lowest cost solution while maintaining adequate performance. Accordingly, a designer generally seeks to balance between cost and performance. There are certain applications, including power supply systems, where extraneous noise in the power supply signal, such as a regulated voltage, can degrade performance below desired operating levels. One way to mitigate such noise is to provide a filter, such as including a low frequency pole.
Low frequency poles are usually implemented with RC networks as they can be more area efficient and usually have a lower cost of implementation. However, in some applications, such as filtering power signals, RC network filters are generally unsuitable because with their high series resistance, they cannot deliver power without a large voltage drop or active components. Additionally, RC networks can generate noise inside their passband. An alternative approach is to employ a network that includes active components, such as transistors, to implement desired filtering. Networks with active components, however, tend to be noisier than their passive counterparts, require a power supply, and are more sensitive to noise present on the power supply.